Recently, there has been considerable interest within the detergent industry for laundry detergents which have the convenience, aesthetics and solubility of liquid laundry detergent products, but retain the cleaning performance and cost of granular detergent products. The problems, however, associated with past granular detergent compositions with regard to aesthetics, solubility and user convenience are formidable. Such problems have been exacerbated by the advent of “compact” or low dosage granular detergent products which typically do not dissolve in washing solutions as well as their liquid laundry detergent counterparts. These low dosage detergents are currently in high demand as they conserve resources and can be sold in small packages which are more convenient for consumers prior to use, but less convenient upon dispensing into the washing machine as compared to liquid laundry detergent which can be simply poured directly from the bottle as opposed to “scooped” from the box and then dispensed into the washing solution.
As mentioned, such low dosage or “compact” detergent products unfortunately experience dissolution problems, especially in cold temperature laundering solutions (i.e., less than about 30° C.). More specifically, poor dissolution results in the formation of “clumps” which appear as solid white masses remaining in the washing machine or on the laundered clothes after conventional washing cycles. These “clumps” are especially prevalent under cold temperature washing conditions and/or when the order of addition to the washing machine is laundry detergent first, clothes second and water last (commonly known as the “Reverse Order Of Addition” or “ROOA”). Such undesirable “clumps” are also formed if the consumer loads the washing machine in the order of clothes, detergent and then water. Similarly, this clumping phenomenon can contribute to the incomplete dispensing of detergent in washing machines equipped with dispenser drawers or in other dispensing devices, such as a granulette. In this case, the undesired result is undissolved detergent residue in the dispensing device.
It has been found that the cause of the aforementioned dissolution problem is associated with the “bridging” of a “gel-like” substance between surfactant-containing particles to form undesirable “clumps.” The gel-like substance responsible for the undesirable “bridging” of particles into “clumps” originates from the partial dissolution of surfactant in the aqueous laundering solutions, wherein such partial dissolution causes the formation of a highly viscous surfactant phase or paste which binds or otherwise “bridges” other surfactant-containing particles together into “clumps.” This undesirable dissolution phenomena is commonly referred to as “lump-gel” formation. In addition to the viscous surfactant “bridging” effect, inorganic salts have a tendency to hydrate which can also cause “bridging” of particles which linked together via hydration. In particular, inorganic salts hydrate with one another to form a cage structure which exhibits poor dissolution and ultimately ends up as a “clump” after the washing cycle. It would therefore be desirable to have a detergent composition which does not experience the dissolution problems identified above so as to result in improved cleaning performance.
The prior art is replete with disclosures addressing the dissolution problems associated with granular detergent compositions. For example, the prior art suggests limiting the use and manner of inorganic salts which can cause clumps via the “bridging” of hydrated salts during the laundering cycle. Specific ratios of selected inorganic salts are contemplated so as to minimize dissolution problems. Such a solution, however, constricts the formulation and process flexibility which are necessary for current commercialization of large-scale detergent products. Various other mechanisms have been suggested by the prior art, all of which involve formulation alteration, and thereby reduce formulation flexibility. As a consequence, it would therefore be desirable to have a detergent composition having improved dissolution without significantly inhibiting formulation flexibility.
Accordingly, despite the disclosures in the prior art discussed previously, it would be desirable to have a granular detergent composition which exhibits improved solubility, has improved flowability and exhibits improved cleaning performance. Also, it would be desirable to have such a detergent composition which exhibits such improved dissolution without significantly inhibiting formulation flexibility.